Sodium carbonate is a widely-used product, with many applications in foods, as well as many other applications such as in cleaning, textile, and other industrial and commercial applications. Much of worldwide sodium carbonate production uses a process known as the “Solvay process”, which involves the reaction of carbon dioxide produced by thermal decomposition of calcium carbonate, with a solution of sodium chloride and ammonia to produce sodium bicarbonate, followed by thermal decomposition of the sodium bicarbonate to form sodium carbonate. However, high capital costs involved with building and operating the Solvay process have invited alternative approaches for making sodium carbonate.
One such alternative type of process is described in U.S. Pat. Nos. 7,708,972, 8,202,659, and US Patent Application Publication 2010/0147698 A1, the disclosure of each of which is incorporated by reference in its entirety herein. This process involves a carbonation reaction between carbon dioxide and an aqueous sodium hydroxide brine solution produced by electrolysis of a sodium chloride solution. Other features of this process include generation of carbon dioxide for the carbonation reaction by reacting calcium carbonate (e.g., from limestone) with hydrochloric acid, and generating the hydrochloric acid by reacting chlorine gas and hydrogen gas produced by the electrolysis. Additional features include separation and purification of the sodium carbonate produced by the carbonation reaction, and recovery and recycle of sodium chloride from the electrolysis byproducts. Although this process can be effective, it also has certain limitations, such as requiring high levels of sodium hydroxide (e.g., at least 25 wt. % concentration) and/or high temperature levels (e.g., above 100° C. or above 110° C.) in order to achieve target efficiency levels.
Many other processes have been used or proposed for the production of sodium carbonate, and each of them has its own advantages and disadvantages. However, new and different processes and systems for producing sodium carbonate, which may afford opportunities for improved performance, cost, reliability, process variation tolerance, etc., are always welcome in the art.